It also looks like there's a manual override switch in the top-right. If you want, you can leave in one or more of either the "off" or "on" tabs depending on if you want this to always be on or off -- that way, if someone (accidentally) switches this on, it'll turn off within at most 24 hours (or vice-versa).
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gregmacFeb 29 '12 at 17:12